Structural Insights Into The Interaction In Solution Between Calmodulin And C-Terminal Fragment Of Calcineurin A Subunit

As the only phosphatase regulated by Calmodulin (CaM), calcineurin (CN) plays an important role in psycological function. However, after many years'related research, the structural information about its calmodulin-binding domain (CBD) and auto-inhibitory domain (AID) still remains unknown, which has set a barrier to the deeper perception about the mechanism of interactions between CNA with CNB and CaM, as well as between CN and its substrates, regulatory factors, and immunosuppressants, and made studies about CN's function more difficult in processes like signal transduction pathways in cellular apoptosis, then will delay the design and improvement of drugs targeting to CN-related diseases like AD and SID.Based on the former research about structural biology, this study aimes to discover the secret by constructing, expressing and purifying the target peptide Ci interacted with CaM, and observing the complex between them in natural state, then the analyzing the conformational change in solution in the way of biophysical methods like CD and NMR. Under the condition of calcium ion, Ci rapidly and completely binds CaM with the ratio of 1∶1 . It is unpractical to determine the 3D structure of Ci in free status because of its disordered conformation and high proportion of random coil, but the conformation has changed regularly after bound by CaM, which may show Ci was in a status of conformational shift from coil to helix. Conformation of CaM has changed greatly after bound by Ci, with the result that the binding sites and interaction module can be roughly determined after chemical shifts assignment, perturbation and calculation of KD, which supports the supposal that CaM and CNA C-terminal were in symmetrical homodimer complex (CaM·Ci)2. In addition, the possible position of"NewCBD"in the scale of residue 430-450 and classification of functional domains in C-terminal have also been discussed.The information about natural interations in solution is necessary enough to offer a brand-new insight into the studies on structural biology about CN, which has been a kind of harassment in related fields, as well as"an addition"to the structural theory of interactions between CaM and its target proteins in future.